Dispensing valves of flexible resilient elastomeric material, particularly liquid silicone rubber, are currently finding application in dispensing packages for a wide variety of fluid products such as beverages, food condiments and body lotions. A package and a valve of this type are disclosed, for example, in U.S. Pat. No. 4,749,108. Current technology for manufacturing valves of this type involves stamping the valve from a sheet of resin material when the material is partially cured, so that the valve retains the shape imparted by the stamping operation following separation from the sheet. This technique involves significant waste of material, which cannot be recycled. The valves are coated with talc to prevent the valves from adhering to each other, and the valves are placed in a vibrator bowl for orientation purposes. Valves fed from the bowl, when properly oriented, are placed in closures for securement to containers after filling. It is therefore a general object of the present invention to provide an injection mold, a mold system and a method of making a dispensing valve that reduce the amount of scrap material and simplify handling of the valves as compared with the current technology described immediately above.
An injection mold for making elastomeric dispensing valves in accordance with one aspect of the present invention includes a first mold section having a core plate with at least one core and a stripper plate having at least one core passage in which the core is slidably received. A second mold section has a cavity plate with at least one passage for feeding elastomeric material through the cavity plate. At least one of the first and second mold sections is movable with respect to the other between an open position in which the first and second mold sections are spaced from each other, and a closed position in which the first and second mold sections are in facing engagement to form at least one mold cavity for molding a dispensing valve between the cavity plate on the second mold section, and the stripper plate and an end of the core on the first mold section. The stripper plate has a vacuum passage for selective application of vacuum to the mold cavity and to a dispensing valve molded in the mold cavity.
A system for molding dispensing valves in accordance with a second aspect of the present invention includes a first mold section and a second mold section, at least one of which is movable with respect to the other between a closed position in which the mold sections form a plurality of dispensing valve mold cavities, and an open position in which the mold sections are spaced from each other and the mold cavities are opened along a mold parting line. A transfer mechanism is movable between the first and second mold sections in the open position of the mold sections for receiving molded valves from the cavities and transferring the valves from between the mold sections. The first mold section in accordance with a preferred embodiment of this second aspect of the invention includes a plurality of vacuum passages for selectively applying vacuum to valves in the mold cavities, first to retain the valves in the cavities when the mold sections are separated and then to permit transfer of the valves from the cavities to the transfer mechanism.
A method of making a dispensing valve in accordance with a third aspect of the present invention includes closing a mold having first and second mold sections and at least one mold cavity formed at a parting line between the mold sections. A dispensing valve is injection molded in the cavity, and the mold sections are then separated along the parting line while applying vacuum to the cavity through the first mold section to retain the molded valve on the first mold section. The molded valve is then contacted by a transfer mechanism, and vacuum is applied to the valve through the transfer mechanism and releasing the vacuum applied to the valve through the first mold section. The valve is then removed from the first mold section by the transfer mechanism. In the preferred implementation of this third aspect of the invention, the valve is injection molded of liquid silicone rubber and allowed to cure within the mold cavity prior to separation of the mold sections, so that the valve retains its molded shape during transfer and further processing.